Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
The process of diffusion! The alveoli are very important in this process, not only because they allow the transfer of oxygen and carbon dioxide, but also because they give the lungs their huge surface area. With all this surface area, they can accomplish their massive task of keeping the body supplied with oxygen.